Hydraulic seal for a gearbox of a tip turbine engine

ABSTRACT

A hydraulic seal for a tip turbine engine includes an inner radial flange and an outer radial flange. The inner radial flange rotates relative to the outer radial seal section and the planet carrier face to prevent lubrication from entering into the air flow streams within the engine without additional engine assembly procedures.

This invention was made with government support under Contract No.:F33657-03-C-2044. The government therefore has certain rights in thisinvention.

BACKGROUND OF THE INVENTION

The present invention relates to a tip turbine engine, and moreparticularly to a non-rotating compartment located along an enginecenterline.

An aircraft gas turbine engine of the conventional turbofan typegenerally includes a forward bypass fan, a compressor, a combustor, andan aft turbine all located along a common longitudinal axis. Acompressor and a turbine of the engine are interconnected by a shaft.The compressor is rotatably driven to compress air entering thecombustor to a relatively high pressure. This pressurized air is thenmixed with fuel in a combustor and ignited to form a high energy gasstream. The gas stream flows axially aft to rotatably drive the turbinewhich rotatably drives the compressor through the shaft. The gas streamis also responsible for rotating the bypass fan. In some instances,there are multiple shafts or spools. In such instances, there is aseparate turbine connected to a separate corresponding compressorthrough each shaft. In most instances, the lowest pressure turbine willdrive the bypass fan.

Although highly efficient, conventional turbofan engines operate in anaxial flow relationship. The axial flow relationship results in arelatively complicated elongated engine structure of considerablelongitudinal length relative to the engine diameter. This elongatedshape may complicate or prevent packaging of the engine into particularapplications.

A recent development in gas turbine engines is the tip turbine engine.Tip turbine engines locate an axial compressor forward of a bypass fanwhich includes hollow fan blades that receive airflow from the axialcompressor therethrough such that the hollow fan blades operate as acentrifugal compressor. Compressed core airflow from the hollow fanblades is mixed with fuel in an annular combustor and ignited to form ahigh energy gas stream which drives the turbine integrated onto the tipsof the hollow bypass fan blades for rotation therewith as generallydisclosed in U.S. Patent Application Publication Nos.: 20030192303;20030192304; and 20040025490.

The tip turbine engine provides a thrust to weight ratio equivalent toconventional turbofan engines of the same class within a package ofsignificantly shorter length.

A gearbox assembly aft of the fan-turbine rotor assembly provides aspeed increase between the fan-turbine rotor assembly and the axialcompressor. A lubricating fluid system of the tip turbine enginesupplies lubricating fluid to the gearbox assembly and other rotatingcomponents. Lubricating fluid systems heretofore utilized in gas turbineengines are inapplicable to a tip turbine engine.

Accordingly, it is desirable to provide a lightweight lubricating fluidsupply system for a tip turbine engine which is compact, relativelyuncomplicated, provides a low part count and is inexpensive tomanufacture yet provides a high degree of reliability.

SUMMARY OF THE INVENTION

A non-rotating compartment for a tip turbine engine according to thepresent invention is defined between an inner support housing, an outersupport housing and an aft housing. The non-rotating compartmentprovides a space that may be utilized for a multitude of engineaccessories and components. As the non-rotating compartment is locatedalong the engine centerline and spaced a distance from the annularcombustor, the non-rotating compartment provides a relatively lowtemperature compartment to receive relatively sensitive components. Thenon-rotating compartment may also enclose an engine lubricating fluidsystem. The non-rotating compartment may alternatively be utilized in itentirety as a lubricating fluid sump or may be still furthercompartmentalized to contain other additional components within theseparate compartments.

The present invention therefore provides a lightweight lubricating fluidsystem for a tip turbine engine which is compact, relativelyuncomplicated, provides a low part count, is inexpensive to manufactureyet provides a high degree of reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features and advantages of this invention will becomeapparent to those skilled in the art from the following detaileddescription of the currently preferred embodiment. The drawings thataccompany the detailed description can be briefly described as follows:

FIG. 1 is a partial sectional perspective view of a tip turbine engine;

FIG. 2 is a longitudinal sectional view of a tip turbine engine along anengine centerline;

FIG. 3 is an expanded view of a lubricating fluid system;

FIG. 4 is an expanded view of a non-rotating cavity of a lubricatingfluid system; and

FIG. 5 is an expanded perspective view of a hydraulic seal of alubricating fluid system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a general perspective partial sectional view of a tipturbine engine type gas turbine engine 10. The engine 10 includes anouter nacelle 12, a nonrotatable static outer support structure 14 and anonrotatable static inner support structure 16. A multitude of fan inletguide vanes 18 are mounted between the static outer support structure 14and the static inner support structure 16. Each inlet guide vanepreferably includes a variable trailing edge 18A.

A nose cone 20 is preferably located along the engine centerline A tosmoothly direct airflow into an axial compressor 22 adjacent thereto.The axial compressor 22 is mounted about the engine centerline A behindthe nose cone 20.

A fan-turbine rotor assembly 24 is mounted for rotation about the enginecenterline A aft of the axial compressor 22. The fan-turbine rotorassembly 24 includes a multitude of hollow fan blades 28 to provideinternal, centrifugal compression of the compressed airflow from theaxial compressor 22 for distribution to an annular combustor 30 locatedwithin the nonrotatable static outer support structure 14.

A turbine 32 includes a multitude of tip turbine blades 34 (two stagesshown), which rotatably drive the hollow fan blades 28 relative to amultitude of tip turbine stators 36 which extend radially inwardly fromthe static outer support structure 14. The annular combustor 30 isaxially forward of the turbine 32 and communicates with the turbine 32.

Referring to FIG. 2, the nonrotatable static inner support structure 16includes a splitter 40, a static inner support housing 42, and a staticouter support housing 44 located coaxial to said engine centerline A.

The axial compressor 22 includes the axial compressor rotor 46 fromwhich a plurality of compressor blades 52 extend radially outwardly anda compressor case 50 fixedly mounted to the splitter 40. A plurality ofcompressor vanes 54 extends radially inwardly from the compressor case50 between stages of the compressor blades 52. The compressor blades 52and compressor vanes 54 are arranged circumferentially about the axialcompressor rotor 46 in stages (three stages of compressor blades 52 andcompressor vanes 54 are shown in this example). The axial compressorrotor 46 is mounted for rotation upon the static inner support housing42 through a forward bearing assembly 68 and an aft bearing assembly 62.

The fan-turbine rotor assembly 24 includes a fan hub 64 that supports amultitude of the hollow fan blades 28. Each fan blade 28 includes aninducer section 66, a hollow fan blade section 72, and a diffusersection 74. The inducer section 66 receives airflow from the axialcompressor 22 generally parallel to the engine centerline A and turnsthe airflow from an axial airflow direction toward a radial airflowdirection. The airflow is radially communicated through a core airflowpassage 80 within the fan blade section 72 where the airflow iscentrifugally compressed. From the core airflow passage 80, the airflowis turned and diffused toward an axial airflow direction toward theannular combustor 30. Preferably the airflow is diffused axially forwardin the engine 10, however, the airflow may alternatively be communicatedin another direction.

A gearbox assembly 90 aft of the fan-turbine rotor assembly 24 providesa speed increase between the fan-turbine rotor assembly 24 and the axialcompressor 22. Alternatively, the gearbox assembly 90 could provide aspeed decrease between the fan-turbine rotor assembly 24 and the axialcompressor rotor 46. The gearbox assembly 90 is mounted for rotationbetween the static inner support housing 42 and the static outer supporthousing 44. The gearbox assembly 90 includes a sun gear shaft 92 whichrotates with the axial compressor 22 and a planet carrier 94 whichrotates with the fan-turbine rotor assembly 24 to provide a speeddifferential therebetween. The gearbox assembly 90 is preferably aplanetary gearbox that provides co-rotating or counter-rotatingrotational engagement between the fan-turbine rotor assembly 24 and anaxial compressor rotor 46. The gearbox assembly 90 is mounted forrotation between the sun gear shaft 92 and the static outer supporthousing 44 through a forward bearing 96 and a rear bearing 98. Theforward bearing 96 and the rear bearing 98 are both tapered rollerbearings and both handle radial loads. The forward bearing 96 handlesthe aft axial loads while the rear bearing 98 handles the forward axialloads. The sun gear shaft 92 is rotationally engaged with the axialcompressor rotor 46 at a splined interconnection 100 or the like.

In operation, air enters the axial compressor 22, where it is compressedby the three stages of the compressor blades 52 and compressor vanes 54.The compressed air from the axial compressor 22 enters the inducersection 66 in a direction generally parallel to the engine centerline Aand is turned by the inducer section 66 radially outwardly through thecore airflow passage 80 of the hollow fan blades 28. The airflow isfurther compressed centrifugally in the hollow fan blades 28 by rotationof the hollow fan blades 28. From the core airflow passage 80, theairflow is turned and diffused by the diffuser section 74 axiallyforward in the engine 10 into the annular combustor 30. The compressedcore airflow from the hollow fan blades 28 is mixed with fuel in theannular combustor 30 and ignited to form a high-energy gas stream. Thehigh-energy gas stream is expanded over the multitude of tip turbineblades 34 mounted about the outer periphery of the fan blades 28 todrive the fan-turbine rotor assembly 24, which in turn drives the axialcompressor 22 through the gearbox assembly 90. Concurrent therewith, thefan-turbine rotor assembly 24 discharges fan bypass air axially aft tomerge with the core airflow from the turbine 32 in an exhaust case 106.A multitude of exit guide vanes 108 are located between the static outersupport housing 44 and the nonrotatable static outer support structure14 to guide the combined airflow out of the engine 10 to provide forwardthrust. An exhaust mixer 110 mixes the airflow from the turbine blades34 with the bypass airflow through the fan blades 28.

Referring to FIG. 3, an engine lubricating fluid system 118 includes anlubricating fluid pump drive gear 120 mounted for rotation with theplanet carrier 94 about the engine axis A. The lubricating fluid pumpdrive gear 120 drives a lubricating fluid pump gear 122 which drives alubricating fluid pump 124 through a shaft 137. The lubricating fluidpump gear 122 is located adjacent the gearbox assembly 90 between thestatic inner support housing 42 and the static outer support housing 44.Preferably, the lubricating fluid pump 124 is located within an aftstatic support structure 45 which is attached to the static innersupport housing 42 and the static outer support housing 44 throughfasteners f such as bolts or the like.

The static inner support housing 42 and the aft static support structure45 define a non-rotating compartment 132 along the engine centerline A(FIG. 4; shaded). The non-rotating compartment 132 provides a spacewhich may be utilized for a multitude of engine accessories andcomponents. As the non-rotating compartment 132 is located along theengine centerline A and displaced from the annular combustor 30 (FIG.2), the non-rotating compartment 132 provides a relatively lowtemperature compartment to receive relatively sensitive components.

Most preferably, the non-rotating compartment 132 encloses the enginelubricating fluid system 118. The engine lubricating fluid system 118 isbut one illustrated example for which the non-rotating compartment 132may be utilized. The non-rotating compartment 132 may be utilized in itsentirety (as illustrated in FIG. 4) as the lubricating fluid sump (FIG.4) or may be still further compartmentalized to contain other enginecomponents.

A lubricating fluid plenum sleeve 134 mounted to the static supportstructure 45 defines an annular lubricating fluid plenum 136 between thelubricating fluid plenum sleeve 134 and an axially extending portion ofthe static support structure 45. The lubricating fluid pump 124 receiveslubricating fluid from within the non-rotating compartment 132 through asupply line 138 (illustrated schematically) which draws lubricatingfluid from the lubricating fluid sump 140 (FIG. 4) defined by thenon-rotating compartment 132.

From the lubricating fluid pump 124 lubricating fluid is communicated tothe annular lubricating fluid plenum 136 through a lubricating fluidfeed line 142 (illustrated schematically) which passes through anliquid-air heat exchanger 145 (one shown) to extract thermal energy fromthe engine lubricating fluid system 118. The lubricating fluid pump 124thereby pressurizes the annular lubricating fluid plenum 136.

The liquid-air heat exchanger 145 is preferably located within atailcone section 128 t of the static support structure 45. Theliquid-air heat exchanger 145 is in communication with a portion of thefan bypass airflow which enters the tailcone section 128 t through anannular tailcone exhaust nozzle entrance E. The liquid-air heatexchanger 145 is located adjacent the engine lubricating fluid system118 and the gearbox assembly 90 to minimize conduit routing paths and totransfer thermal energy into the combined airflow out of the engine 10to recover thrust loss ducted from the fan bypass stream through theannular tailcone exhaust nozzle entrance E. That is, the fan bypassairflow receives thermal energy from the heat exchanger 145 whichincreases engine efficiency. It should be understood that otherliquid-air heat exchanger locations may also be utilized by the instantinvention.

Lubricating fluid within the annular lubricating fluid plenum 136 iscommunicated through the static support structure 45 by way of amultitude of lubricating fluid passages 144, 146, 148 (one of eachshown). It should be understood that any number of passages may beutilized with the instant invention. The lubricating fluid passages 144,146, 148 are directed toward the gearbox assembly 90. Preferably,lubricating fluid passages 144, 146, 148 are respectively directedtoward a multitude of forward planet bearing passages 150 (one shown), amultitude of sun gear passages 152 (one shown), and a multitude of aftplanet bearing passage 154 (one shown). It should be understood thatalthough only one of each of the multitude of the passages areillustrated, multiple passages 150, 152, 154 radially displaced aboutthe engine axis A will be located at the same axial position as thepassages 144, 146, 148 along engine axis A. That is, although thelubricating fluid passages 144, 146, 148 are through the static supportstructure 45 which is fixed in rotation, the multitude of passages 150,152, 154 are being rotated directly adjacent, and preferably each withina common plane of each passage 156, 158, 160. It should be understoodthat the passages need not be directly opposed.

Lubricating fluid is essentially sprayed under pressure from within theannular lubricating fluid plenum 136 through the lubricating fluidpassages 144, 146, 148 and into the multitude of passages 150, 152, 154as they revolve thereby. Lubricating fluid from the multitude ofpassages 150, 152, 154 is thereby communicated respectively to amultitude of forward planet bearings 162 (one shown), a sun gear 164mounted to the sun gear shaft 92, and an aft planet bearing 166 (oneshown). Lubricating fluid is thereby communicated directly into thegearbox assembly 90 without heretofore static/rotating transferinterfaces.

Lubricating fluid is also communicated to the forward bearing assembly68 and the aft bearing assembly 62 through respective oil feeds 168,168′. The oil feeds 168, 168′ preferably communicate lubricant from thelubricating fluid feed line 142.

Lubricating fluid is then returned to the lubricating fluid sump 140through a drain passage d (other drain passages d shown in FIG. 1).Notably, the drain passages are for an engine operated in a verticalflight mode. Should the engine be operated horizontally, the oil drainsystem is according adjusted such as by proving a scavenge pump withdrain lines running to other areas.

Referring to FIG. 5, a hydraulic seal 170 is preferably located forwardof the gearbox assembly 90 to maintain the lubricating fluid in thegearbox assembly 90 by preventing lubricating fluid from travelingaxially forward toward the fan hub 64. The hydraulic seal 170 provides abarrier formed by blockage of lubricating fluid to prevent thelubricating fluid from migrating away from the rotating components. Thehydraulic seal 170 is essentially formed by lubricating fluid fillingthe gap between the inner radial flange 171 and the planet carrier face180 which is held in place by the centrifugal force from the spinningseal assembly.

The hydraulic seal 170 includes an inner radial flange 171 and an outerradial flange 172. The inner radial flange 171 extends radially from thesun gear shaft 92 which rotates with the axial compressor 22 (FIG. 2).The outer radial flange 172 rotates with planet carrier 94 which rotateswith the fan-turbine rotor assembly 24 (FIG. 2). Oil does not enterinside of the axial compressor. This area is maintained oil free. Thehydraulic seal prevents high pressure, hot air from entering the gearboxassembly 90 and also maintains oil within the gearbox assembly 90.

The inner radial flange 171 at least partially radially overlaps theouter radial flange 172. The inner radial flange 171 is a relativelyflat annular disk which is integrally formed with the sun gear shaft 92.The outer radial flange 172 is preferably step-shaped in cross-section.The outer radial flange 172 includes an axial fan hub section 174, aradial mount section 176 extending from the axial fan hub section 174,and an outer radial seal section 178 extending from the axial fan hubsection 174. The radial mount section 176 is parallel to a planetcarrier face 180 of the planet carrier 94 and is preferably attachedthereto through a fastener 182 such as a bolt or the like. The fastener182 is preferably the same fastener 182 which mounts the fan-turbinerotor assembly 24 to the planet carrier 94 of the gearbox assembly 90.

The inner radial flange 171 extends between the outer radial sealsection 178 and the planet carrier face 180 to form a hydraulic seal.The inner radial flange 171 rotates relative to the outer radial sealsection 178 and the planet carrier face 180 to maintain lubricatingfluid within the gearbox assembly 90 (FIG. 4). The hydraulic seal 170prevents lubricating fluid from entering into the air flow streamswithin the engine 10 without additional engine assembly procedures. Thatis, the air pressure from the last stage of the axial compressorbalances with the oil pressure created by the spinning seal cavity.

It should be understood that relative positional terms such as“forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like arewith reference to the normal operational attitude of the vehicle andshould not be considered otherwise limiting.

The foregoing description is exemplary rather than defined by thelimitations within. Many modifications and variations of the presentinvention are possible in light of the above teachings. The preferredembodiments of this invention have been disclosed, however, one ofordinary skill in the art would recognize that certain modificationswould come within the scope of this invention. It is, therefore, to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described. For thatreason the following claims should be studied to determine the truescope and content of this invention.

1. A gearbox assembly for a gas turbine engine having a fan-turbinerotor assembly comprising: a nonrotatable support structure mountedabout an engine centerline; a gear shaft mounted about said nonrotatablesupport structure for rotation about said engine centerline; an innerradial flange extending from said gear shaft; a planet carrier mountedfor rotation about said engine centerline; and an outer radial flangewhich extends from said planet carrier for rotation relative to saidinner radial flange, said outer radial flange including a radial mountsection, an axial fan hub section which extends transverse to saidradial mount section, and an outer radial seal section which extendstransverse to said axial fan hub section, said outer radial seal sectionat least partially radially overlapping said inner radial flange to forma hydraulic seal, said outer radial flange mountable to the fan-turbinerotor assembly for rotation therewith to mount said fan-turbine rotorassembly to the gearbox assembly.
 2. The gearbox assembly as recited inclaim 1, wherein said outer radial flange is mounted to said planetcarrier with a fastener.
 3. The gearbox assembly as recited in claim 1,wherein said outer radial flange is bolted to said planet carrier. 4.The gearbox assembly as recited in claim 1, wherein said outer radialflange is stepped-shaped in cross-section.
 5. The gearbox assembly asrecited in claim 1, wherein said outer radial seal section is parallelto a planet carrier face of said planet carrier.
 6. The gearbox assemblyas recited in claim 1, wherein said outer radial flange is mounted witha fastener common to said fan-turbine rotor assembly.
 7. The gearboxassembly as recited in claim 1, further comprising an axial compressorwhich rotates with said gear shaft.